EUROPEAN PRESSURE ULCER ADVISORY PANEL

Pressure ulcer prevention in x-ray departments
Audrey Brown
Derry, UK

Purpose
The time a patient spends on an X-ray table is increasing as procedures become more complex with increasing interventional radiology, therefore there is a growing need to look at the risk of pressure damage occurring. It has been suggested but not proven that a patient in this hospital developed a pressure sore during a prolonged Computed Tom-ography (CT) Guided Biopsy, which was noticed on return to the ward. This project aimed to assess the situation.

Method
This prospective study collected data from 80 patients, 20 patients on each of the four different mattresses/support surfaces used in our department. Data was collected to assess each patients risk of pressure damage and a risk assessment score determined using the Braden Scale. A skin inspection of eleven pressure areas pre and post examination was documented and duration of examination noted.

Results
53.8% acquired Stage 1 or –1 skin damage in the immediate post examination period. Logistic regression analyses indicated that the effectiveness of the 4 mattresses differed. The closed foam mattress used for patients undergoing angiography was most effective for preventing skin changes/worsening of any kind. The risk of patient as measured by Braden Scale was found to be significant. Relative to a patient judged at no risk, a high-risk patient was 19.99 times as likely (P=0.0010) to exhibit worsening of any kind and 40.36 times (P+0.004) as likely to exhibit worsening at the sacrum.

Conclusion
A potential risk appears to exist for pressure damage occurring in a radiology department. The length of time a patient lies on the X-ray table mattress is not the contributory factor but whether they are at risk of developing pressure area damage as measured by a risk assessment tool. Difference in type of mattress needs to be addressed.
Key words: Pressure sore, radiology, mattress/support surface, risk assessment, evidence-based documentation, patient care.

Evaluation of alternating pressure air mattresses using a time-based pressure threshold technique and laser Doppler micro-vascular perfusion measurements on the heel
Shyam Rithalia
University of Salford, Salford, UK
Linda Russell
Queens Hospital, Derbyshire, UK

Introduction
Heels have substantially higher tissue interface pressures and are prone to ulceration compared to other bony prominences. Although many different type of APAMs are used for the prevention and treatment of pressure ulcers, few high quality randomised controlled trials (RCTs) are available on which to base purchasing decisions. Faced with this situation, physiological measurements are increasingly being used as a surrogate. We have previously reported a time-based technique1, which calculates pressure relief index (PRI), for analysing the ability of such systems, and have demonstrated that different designs produce variable results in this regard. The present study compares the pressure relieving characteristics of two (Nimbus3, Huntleigh Healthcare Ltd and Duo, Hill-Rom Ltd) using PRI and blood perfusion measurements.

Methods
A total of eleven healthy adult volunteers (eight males, three females) participated in the investigation for interface pressure and blood perfusion measurements. They were recruited from postgraduate students and staff of the University of Salford. Their written consent was obtained prior to the commencement of the measurements in a temperature regulated (23 – 25°C) room. They were asked to lie supine on the bed, whilst wearing normal light clothing. Care was used to place both left and right heels on the centre of the same air cell of a mattress. Interface pressure (IP) transducer (OPM, model II, Talley Group Ltd, Hants, UK) was placed under the right heel and laser Doppler (LD) probe (Softflo, model BPM2, Vasamedics Inc, MN, USA) on the left heel. Blood perfusion was reported in arbitrary units (AU) following zero calibration. Measurements of IP and LD were taken simultaneously over at least two alternating cycles, as well as mattress air pressure. Differences between various pressures and blood perfusion LD values over one cycle were analysed using Student’s t-test or the Mann Whitney U-test depending on whether or not data were normally distributed. A difference was considered significant when p < 0.05.

Results
The Nimbus3 provided consistently lower IPs during deflation phase of the cycle (Nimbus3 = 20.2 ( 8.9 mm Hg and Duo = 68.5 (13.0mm Hg; p < 0.001). The time intervals calculated over 60 minutes when IP remained below arbitrarily chosen thresholds of 30 and 20mm Hg were 10 and 3 minutes respectively for the Nimbus. The Duo achieved zero time below either threshold. There was no significant difference in peak pressures under the heel despite the Duo offering significantly lower (P< 0.001) air cell pressures in the heel region. Skin LD levels integrated over time were significantly greater (p < 0.001) for the Nimbus (10171.3 ± 6721.5 AU) compared with those for the Duo (6721.5 ± 1588.2 AU).

Summary
Based on the present combined results of IP and blood perfusion in healthy subjects, it appears that, to produce hyperaemic reaction in the skin tissue or re-perfusion after loading an appropriate course of action is to provide periodic complete or near complete off-loading. A previously published clinical study supports this finding.2 It is also important to note that low air cell pressures do not necessarily produce lower IPs under the heel, contrary to the intuitive classical notion.

Reference
Rithalia SVS, Gonsalkorale M. Journal of Rehabilitation Research and Development 1998; 35: 225– 230.
2. Russell L. Reynolds TM. Journal of Wound Care 2000; 9: 52–55.

Change of Body Pressure and Shear Force at Head Up / Down Motion
Takehiko Ohura1, Makoto Takahashi2, Maki Mimura3 and Ryuji Kajiwara3
1) Pressure Ulcers and Wound Healing Research Center, Keishokai, Sapporo, Japan
2) Biomedical Systems Engineering, Hokkaido University, Sapporo, Japan
3) Molten Corporation, Hiroshima, Japan

Introduction
Recently in Japan, pressure ulcers have been thought to be caused by the factors: mechanical stress x time x frequency
rather than just the pressure of the body surface x time.
Until today it has been clinically difficult to measure direct shear force, however, due to our design and development of a new electrical device we have been able to measure shear force and surface pressure simultaneously, allowing us to obtain some excellent data.

Method
1. Measurement of three points
1) Bone prominence of sacral vertebra
2) 25cm above from the middle of sacral vertebra
3) Middle of upper thigh.

2. Method
Subjects lay on a normal hospital mattress with a bed pad and a cotton sheet. A sensor pad was directly applied to the subjects skin and then dressed in cotton underwear. In both knees elevated and non-elevated positions continuing measurements were taken of the upper body shear force when raised from 30° through to 80°.

Results
1. As the upper body is raised the shear force on the sacral region changes the direction between the upper and lower body.
2. Change of shear force was found in both knees elevated and non-elevated positions before upper body was also raised.
3. Change of shear force was evident through the entire rotation between the 30° and 80° upper- body elevated position.
4. Residual shear force was surprisingly detected when the upper body was lowered.

Summary
The use of an electrical device developed in Japan, which measures the shear force has allowed us to clinically obtain a great amount of critical new data and evidence.

Numerical Accuracy of pressure mapping systems – a comparative evaluation
P. Diesing, D. Hochman and U. Boenick
Technical University Berlin, Department of Mechanical Engineering, Berlin, Germany

Introduction
Pressure mapping systems (PMS) has been established over the last decade for to evaluate the influence of pressure on the development of pressure ulcers (PU). Mat integrated sensor-arrays based on resistive and capacitive effect became the state of the art against the older pneumatic systems. Although the pressure measurement between the skin and the surface of the bed or wheelchair is only an indicator for the pressure inside the tissue, PMS seem to be the best way to evaluate the risk created by pressure for PU in an region of interest. For to choose i.e. an optimal seat-cushion for a wheelchair it might be enough, to compare the pictures of an PMS to find the best cushion. For to define a lab-procedure to check pressure relieving devices concerning their effectiveness to prevent PU it is necessary to know the measurement errors creates by linearity, hysteresis, hammocking-effect and effects of non sufficient resolution of the PMS. The main issue of this paper is, to show the results of a short comparative evaluation of the actual commercial offered PMS.

Methods
Four PMS (FSA, novel, Seatscan, Xsensor) had been evaluated at the TU Berlin, Dep. Biomechanical Engineering. The systems had been calibrated by the manufacturer directly before the mat was brought in. The systems had been tested in regard to accuracy and linearity of a small area influenced by the geometry of the force applicator, the hammocking-effect on different surfaces (hard ground and two different foams) and hysteresis. Because of the different resolutions of the sensormats we decided to compare calculated normal forces instead of the measured pressure.

Results
Three systems (FSA, novel and Xsensor) has been integrated in the comparison. The Seatscan-system was demonstrated with a 6 year old sensormat and the linearity showed a curve which was not feasible, so the Seatscan system was excluded from the comparison.

All systems showed a good linearity, even if there was a relevant difference between mats with high resolution (32 x 32 sensors) and systems with low resolution (16 x 16 sensors). The size of the applicator had an important effect on the readings of the normal force. All PMS underestimated the force applied on a small contact area. The minimum contact area for an accurate measurement was in the range between 4.5cm2 and 19.6cm2. The influence of the ham-mocking effect on the readings could be observed as expected. The readings differed between the hard surface and a soft foam underlay. The measured hysteresis curves differed in part from curves measured in previous studies.

Summary
The evaluated PMS are excellent tools for the visualization of the pressure in the daily use of a hospital. They allow in a very quick and very easy way to find the area, where high pressures increase the risk of getting an PU and how this pressure is influenced by different devices. The software produces some analysis of the measured data in a comfortable way. However, for the numerical measurement of high pressure peaks under bones PMS underestimate the pressure, because of insufficient resolution and other effects. Additionally the difference between the readings of different types of PMS will not allow to compare values measured with different systems.

The moist wound environment is a well known concept in the treatment of wounds. Many dressings reflect this concept and are used to enhance healing. It is not clear to what degree the various dressings are capable of influencing the moisture retention of the skin and whether they vary in effectiveness. In addition, problems such as maceration of the surrounding skin have been reported when using dressings that promote a moist wound environment.

The aim of this study was to measure the ability of various dressings to maintain a moist wound environment by investigating moisture retention within the skin.

The moisture retention in the horny layer of the surrounding skin of 38 pressure ulcers was measured. Measurements were carried out within 1cm of the wound area. The control was non-treated exposed skin away from the wound area. Four types of wound dressing and two kinds of ointment with gauze dressing were used on 38 wounds. The measurements were carried out using Moisture Checker MY707S (Scalar Corp., Japan).

The dressings used were as follows: hydrocellular polyurethane foam (Allevyn™, Smith & Nephew); hydropoly-mer (Tielle™, Johnson & Johnson); hydrogel (Intrasite Gel™, Smith & Nephew); hydrofiber (Aquacel™, Conva-Tec); bucladesine sodium ointment (Actosin™, Daiichi Pharm.); and silver sulfadiazine cream (Geben Cream™, Mitsubishi-Tokyo).

Once the dressings were removed from the wound, the area was wiped with a dry gauze and measured in the same spot three times. An average for each spot was then calculated. The locations of the pressure ulcers were as follows: 20 sacrum, 9 heel, 7 greater tochanter and 2 others.

The measurements of the surrounding skin area were compared with the average moisture rate of the horny layers. The moisture retention score for each dressing from the highest to the lowest was as follows: hydrofiber, hydrogel, and polyurethane foam. For the hydropolymer dressing was the moisture rate score was actually lower under the dressing than in the control area (see table below).

Conclusion
The hydrocellular polyurethane foam dressing and the hydrogel appeared to enable good moisture retention. The hydropolymer dressing appeared to create a dry environment. These results were also evident from visual inspection.
Strategies to identify the most appropriate dressing for a wound should take into account the effect of the dressing on skin moisture retention and the potential to dry out a wound or keep it too moist, and possibly cause maceration.